558
FXUS65 KBYZ 171922
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
122 PM MDT THU SEP 17 2026
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON
AND EVENING. LOCALLY HEAVY RAIN POSSIBLE OVER SE MONTANA WITH
ANY SHOWERS/THUNDERSTORMS.
- A FEW STRONG THUNDERSTORMS ARE POSSIBLE, MAINLY AROUND AND EAST
OF BILLINGS FRIDAY AFTERNOON AND EVENING.
- FLOOD WATCH FRIDAY NIGHT THROUGH SUNDAY FOR MUCH OF THE AREA. WIDESPREAD
PRECIPITATION FRIDAY AFTERNOON THROUGH THE WEEKEND, WITH THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL WIDESPREAD THROUGH SATURDAY
NIGHT.
- CHANCE FOR AT LEAST AN INCH OF RAINFALL IS GREATER THAN 90
PERCENT ACROSS MUCH OF SOUTHERN MONTANA AND NORTHERN WYOMING.
THE CHANCE FOR AT LEAST 2 INCHES OF RAINFALL IS 50 TO 70
PERCENT, GREATEST ACROSS SOUTH-CENTRAL MONTANA.
DISCUSSION
REST OF TODAY THROUGH WEDNESDAY...
A FLOOD WATCH HAS BEEN ISSUED FOR ALL EXCEPT FALLON, CUSTER,
AND CARTER COUNTIES, FROM FRIDAY EVENING THROUGH THE DAY SUNDAY.
FORECAST TRENDING MORE UNSETTLED THIS AFTERNOON THROUGH THIS
WEEKEND, WITH THE FLOOD POTENTIAL INCREASING FOR CENTRAL AND
WESTERN PORTIONS OF THE FORECAST AREA. THE AREA IS CURRENTLY UNDER
SOUTHERLY DIFFLUENT FLOW WRAPPING AROUND A DEEPENING UPPER LOW
OVER THE CA/NV/OR TRIPLE POINT. AT THE SURFACE SOUTHEASTERLY
WINDS GUSTING TO 30 MPH OVER SOUTHEAST MT ARE PULLING SUBSTANTIAL
PLAINS MOISTURE INTO THE AREA. BY THIS EVENING, PRECIPITABLE WATER
VALUES WILL BE PUSHING 4 STANDARD DEVIATION ABOVE NORMAL (220% OF
NORMAL) OVER SE MONTANA, AND BY SATURDAY MORNING VALUES OF
220-240% OF NORMAL WILL BE WIDESPREAD ACROSS THE FORECAST AREA.
THE UPPER LOW TO THE WEST WILL DRIFT SLOWLY THIS DIRECTION OVER
THE NEXT 36 HOURS AND THEN TRACK ACROSS CENTRAL WYOMING THIS
WEEKEND, EXITING TO THE EAST ON MONDAY. THIS TRACK IS THE BEST
PRECIPITATION PATTERN FOR OUR AREA AND COMBINED WITH THE HIGH
ATMOSPHERIC MOISTURE VALUES IS PRIMED TO BRING AT LEAST LOCALLY
HEAVY RAINFALL TO THE REGION, IF NOT AREAS OF HEAVY RAINFALL. THE
LATEST MODEL RUNS HAVE COME INTO VERY GOOD AGREEMENT WITH THE
STORM TRACK AND PRECIPITATION INTENSITY.
NBM 48HR PROBABILITIES FOR OVER 1 INCH OF PRECIPITATION FRIDAY
NIGHT THROUGH SUNDAY ARE IN THE 80-100% RANGE FOR MOST OF THE
FORECAST AREA, WITH 2 INCH PROBABILITIES OF 50-70% FROM ROSEBUD
COUNTY WEST INTO THE FOOTHILLS. THE NBM MEAN PRECIPITATION FOR THE
SAME 48 HOUR PERIOD RANGES FROM 1.7 INCHES IN LIVINGSTON, 2.3
INCHES IN COLUMBUS, 2.2 INCHES IN BILLINGS, 1.9 INCHES
HARDIN/COLSTRIP, AND 1.6 INCHES IN SHERIDAN. GOING TO THE HIGH END
OF THE NBM (90TH PERCENTILE) BRINGS IN AREAS OF 3 TO 4 INCHES OF
RAINFALL, LIKELY IN AREAS WHERE THUNDERSTORMS DEVELOP AND TAP
INTO THAT HIGH ATMOSPHERIC MOISTURE. AS A RESULT OF THE ABOVE HAVE
ISSUED A FLOOD WATCH FOR THE WEEKEND. THE MEAN RAINFALL OVER A
COUPLE OF DAYS IS PROBABLY ONLY A MINOR IMPACT, BUT THE HIGHER
POTENTIAL THAT COULD DOUBLE THOSE MEAN VALUES IN SOME AREAS WOULD
BE A HIGHER IMPACT FLOOD SCENARIO.
RECENT BURN SCARS WILL BE HIGHLY SUSCEPTIBLE FOR FLASH FLOODING
AND DEBRIS FLOWS IN THE CURRENT LONG DURATION PRECIPITATION
FORECAST, ESPECIALLY IF THUNDERSTORM PRECIPITATION IMPACTS THEM.
THOSE LIVING NEAR RECENT BURN SCARS SHOULD HAVE A PLAN OF ACTION
TO SEEK SAFETY SHOULD THE HEAVY RAINFALL DEVELOP IN THOSE
LOCATIONS. PAY ATTENTION TO LOCAL OFFICIALS DIRECTIONS AND FOR ANY
FLASH FLOOD WARNINGS THAT MAY BE ISSUED.
THERE STILL LOOKS TO BE A WINDOW FOR A FEW STRONGER THUNDERSTORMS
ON FRIDAY AFTERNOON/EVENING FOR AREAS FROM BILLINGS EAST INTO SE
MONTANA. SHEAR PROFILES DO NOT LOOK AS STRONG AS THEY DID
YESTERDAY, BUT WITH SUN EARLY IN THE DAY ALLOWING TEMPERATURES
INTO THE LOWER 80S ALONG WITH THE STRONG PWATS, CAPE VALUES WILL
BE SUPPORTIVE OF HAIL AND GUSTY WINDS TO GO ALONG WITH VERY HEAVY
RAINFALL. THOSE WITH OUTDOOR AND SPORTS VIEWING PLANS SHOULD PAY
ATTENTION TO THE FORECAST AND BE PREPARED IN CASE A STRONG STORM
DEVELOPS IN YOUR VICINITY TOMORROW.
PRECIPITATION SHOULD TAPER OFF SUNDAY NIGHT INTO MONDAY FROM WEST
TO EAST AS THE UPPER LOW MOVES INTO THE NORTHERN PLAINS STATES.
WHILE MUCH DRIER WEATHER IS FORECAST FOR NEXT WEEK, DEPENDING ON
HOW MUCH RAIN FALLS THIS WEEKEND, THERE WILL PROBABLY BE A GOOD
CHANCE FOR AT LEAST AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS EACH DAY INTO MID-WEEK JUST FROM THE RESIDUAL
SURFACE MOISTURE ACROSS THE REGION.
SNOWFALL...WITH THE INCREASED PRECIPITATION FORECAST, SNOW
AMOUNTS IN THE HIGHEST PEAKS OF AREA MOUNTAINS HAVE CLIMBED INTO
THE 3 TO 6 INCH RANGE. SNOW LEVELS START OUT AROUND 12KFT FRIDAY
NIGHT, DROPPING TO 11KFT SATURDAY AFTERNOON AND POSSIBLY FALLING
TO AROUND 10KFT SATURDAY NIGHT, WHICH IS A BIT LOWER THAN
PREVIOUS FORECASTS. MAY STILL NEED A WINTER WEATHER ADVISORY FOR
THE BEARTOOTH PASS WITH THIS SYSTEM, BUT LOOKS LIKE IT WOULD BE
SATURDAY NIGHT INTO SUNDAY MORNING, SO WILL HOLD OFF ON THAT FOR
NOW. THAT SAID, ANYONE PLANNING TRAVEL OVER THE PASS THIS WEEKEND
SHOULD BE PREPARED FOR WINTER CONDITIONS.
TEMPERATURES WILL REACH THE 75 TO 85 DEGREE RANGE ON FRIDAY,
WARMEST OVER THE EAST. HIGHS WILL BE MAINLY IN THE 60S WITH THE
WIDESPREAD PRECIPITATION SAT/SUN. 70S WILL BE COMMON THE REST OF
NEXT WEEK. CHAMBERS
AVIATION
BREEZY SOUTHEASTERLY WINDS HAVE DEVELOPED OVER FAR EASTERN
MONTANA TODAY, AND ARE EXPECTED TO CONTINUE THROUGH THIS EVENING
BEFORE BACKING OFF TONIGHT. WITH THIS, WIND GUSTS IN THE 20S TO
30S KNOTS ARE FORECAST, STRONGEST AROUND KBHK AND K97M.
THIS AFTERNOON AND EVENING, SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE FORECAST TO DEVELOP AND MOVE NORTHEAST THROUGH
PORTIONS OF THE AREA. WHILE CONFIDENCE IS LOW ON ANY IMPACTS TO
TERMINALS, GUSTY WINDS AND BRIEF HEAVY RAIN REDUCING VISIBILITY
ARE THE MAIN CONCERNS TODAY. LOOK FOR THIS ACTIVITY TO DIMINISH
THIS EVENING INTO TONIGHT.
FOG IS POSSIBLE TONIGHT INTO FRIDAY MORNING OVER EASTERN MONTANA
AND NORTHERN WYOMING (MEDIUM CHANCE). THIS INCLUDES AIRFIELDS
AROUND KMLS, KBHK, K97M, AND KSHR. ANY FOG THAT DEVELOPS SHOULD
LIFT AROUND 14Z TO 16Z FRIDAY. LA
PRELIMINARY POINT TEMP/POPS
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 056/080 057/063 053/070 051/074 052/078 052/077 051/077
24/T 99/T 87/T 20/B 00/U 11/U 11/U
LVM 052/075 050/060 047/071 045/075 047/076 047/076 047/076
27/T 99/T 85/T 20/U 01/U 11/U 11/U
HDN 054/082 056/066 051/070 048/075 047/079 046/079 045/080
15/T 9+/T 88/T 30/B 00/U 10/U 01/U
MLS 058/082 058/066 054/065 052/073 052/078 053/079 052/079
11/U 69/T 98/W 31/B 00/U 11/U 00/U
4BQ 056/081 057/067 053/064 051/071 051/078 053/078 052/080
42/B 78/T 99/T 52/W 00/U 21/U 10/U
BHK 056/078 053/066 050/063 047/070 048/076 049/079 049/079
31/B 27/T 98/T 31/E 10/B 11/U 11/U
SHR 052/080 053/066 048/065 045/073 044/077 045/078 045/079
15/T 9+/T 99/T 52/W 00/U 12/W 11/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH IN EFFECT FROM FRIDAY EVENING THROUGH SUNDAY
AFTERNOON FOR ZONES
29>31-34-36-40-42-56>58-63>68-138-139-141-169>173-228-235.
WY...FLOOD WATCH IN EFFECT FROM FRIDAY EVENING THROUGH SUNDAY
AFTERNOON FOR ZONES 198-199.
WEATHER.GOV/BILLINGS
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